(1) Field of the Invention
The present invention relates to a cyclopropane compound having orexin receptor antagonism or a pharmaceutically acceptable salt thereof, and a medicinal use thereof. The present invention also relates to a pharmaceutical composition comprising the above-mentioned compound as an active ingredient.
(2) Description of Related Art
Orexin-A (OX-A, consisting of 33 amino acid peptides) and orexin-B (OX-B, consisting of 28 amino acid peptides), two types of intracerebral neuropeptides, which are expressed by neurons localized at the hypothalamus in the brain, have been discovered (Patent Document 5 and Non-Patent Document 1) as endogenous ligands of G protein-coupled receptors mainly existing in the brain, namely, orexin receptors (Patent Documents 14). It has been known that such orexin receptors include two subtypes, namely, an OX1 receptor (OX1) as a type 1 subtype and an OX2 receptor (OX2) as a type 2 subtype. OX1 binds OX-A more selectively than OX-B, and OX2 is able to bind OX-A as well as OX-B. Orexin has been found to stimulate the food consumption of rats, and thus, it has been suggested that orexin would play a physiological role as a mediator in a central feedback mechanism for controlling feeding behavior (Non-Patent Document 1). On the other hand, it has been observed that orexins control sleep-wake conditions. Thus, it is considered that orexins will potentially lead to new therapies for narcolepsy, as well as for insomnia and other sleep disorders (Non-Patent Document 2). In addition, it has been suggested that orexin signals in the ventral tegmental area regarding neural plasticity associated with opioid dependence and nicotine dependence play an important role in vivo (Non Patent Document 3 and Non Patent Document 4). It has been also reported that OX2 receptor was selectively inhibited to alleviate ethanol dependence in experiment using rats (Non Patent Document 5). Moreover, it has been reported that corticotropin-releasing factor (CRF), whichinvolved in depression and anxiety disorder, is involved in orexin-induced behaviors in rats, and that orexin may play an important role in some stress reactions (Non Patent Document 6).
Orexin receptors are found in the mammalian brain and may have numerous implications in pathologies such as depression; dysphoria; anxiety; addictions, obsessive compulsive disorder; affective neurosis; depressive neurosis; anxiety neurosis; dysthymic disorder; mood disorder; sexual dysfunction; psychosexual dysfunction; sex disorder; schizophrenia; manic depression; delirium; dementia; severe mental retardation and dyskinesias such as Huntington's disease and Tourette syndrome; eating disorders; sleep disorders; cardiovascular diseases, diabetes; appetite/taste disorders; vomiting/nausea; asthma; Parkinson's disease; Cushing's syndrome/disease; basophil adenoma; prolactinoma; hyperprolactinemia; hypopituitarism; hypophysis tumour/adenoma; hypothalamic diseases; inflammatory bowel disease; gastric dyskinesia; gastric ulcers; Froehlich's syndrome; hypophysis diseases, hypothalamic hypogonadism; Kallman's syndrome (anosmia, hyposmia); functional or psychogenic amenorrhea; hypopituitarism; hypothalamic hypothyroidism; hypothalamic-adrenal dysfunction; idiopathic hyperprolactinemia; hypothalamic disorders of growth hormone deficiency; idiopathic growth deficiency; dwarfism; gigantism; acromegaly; disturbed biological and circadian rhythms; sleep disturbances associated with diseases such as neurological disorders, neuropathic pain and restless leg syndrome; heart and lung diseases, acute and congestive heart failure; hypotension; hypertension; urinary retention; osteoporosis; angina pectoris; myocardial infarction; ischemic or haemorrhagic stroke; subarachnoid haemorrhage; ulcers; allergies; benign prostatic hypertrophy; chronic renal failure; renal disease; impaired glucose tolerance; migraine; hyperalgesia; pain; enhanced or exaggerated sensitivity to pain such as hyperalgesia, causalgia, and allodynia; acute pain; burn pain; atypical facial pain; neuropathic pain; back pain; complex regional pain syndrome I and II; arthritic pain; sports injury pain; pain related to infection e.g. HIV, post-chemotherapy pain; post-stroke pain; post-operative pain; neuralgia; conditions associated with visceral pain such as irritable bowel syndrome, migraine and angina; urinary bladder incontinence e.g. urge incontinence; tolerance to narcotics or withdrawal from narcotics; sleep apnea; narcolepsy; insomnia; parasomnia; and neurodegenerative disorders including nosological entities such as disinhibition-dementia-parkinsonism-amyotrophy complex; pallido-ponto-nigral degeneration epilepsy; seizure disorders and other diseases related to general orexin system dysfunction.
(2R)-2-{(1S)-6,7-dimethoxy-1-[2-(4-trifluoromethyl-phenyl)ethyl]-3,4-dihydro-1H-isoquinolin-2-yl}-N-methyl-2-phenylacetamide (ACT-078573; almorexant), a compound that functions as an orexin receptor antagonist, had been clinically developed as a therapeutic agent for insomnia (Patent Document 6). This compound causes a decrease in wakefulness in rats, which is characterized by decreased functions of awakening and spontaneous locomotor activity, and it dose-dependently increases both rapid eye movement (REM) sleep time and non-REM sleep time, and this compound, when administered to normal humans, exhibits dose-dependently a reduction of sleep latency, sleep efficacy and extension of total sleep time (Non Patent Document 7). Thereis is also an article reporting that the compound, when administered to patients with insomnia, exhibits improvement of sleep efficacy, shortness of sleep latency, increase of REM sleep and improvement of REM sleep ratio (Non Patent Document 8). Furthermore, it has also been described that this compound improves the memory function of model rats (Patent Document 7), and that the compound is effective for posttraumatic stress disorder (Patent Document 8). On the other hand, 5-chloro-2-{(5R)-5-methyl-4-[5-methyl-2-(2H-1,2,3-triazol-2-yl)benzoyl]-1,4-diazepan-1-yl}-1,3-benzoxazole (MK-4305; suvorexant, Patent Document 9) and MK-6096, which have dual orexin antagonisms against OX1 and OX2, have been clinically developed as a medicine for insomnia.